In recent years, there has been growing demand for a flat panel display with an information network advanced. As the flat panel display, the following displays have been known, for example: a non light-emitting liquid crystal display (LCD), a light-emitting plasma display (PDP), an inorganic electroluminescence (inorganic EL) display, and an organic electroluminescence (EL) display. Among these flat displays, the organic EL display has been significantly advanced.
In a field of the organic EL display, the following two techniques have been known: (i) a technique of displaying a moving image by simple matrix driving, and (ii) a technique of displaying a moving image by causing organic EL elements to be subjected to active matrix driving with the use of a thin film transistor (TFT).
Further, according to a conventional display, a red pixel for emitting red light, a green pixel for emitting green light, and a blue pixel for emitting blue light are adjacently provided as one unit, so as to provide a full color image by creating various colors, e.g., a white color.
In order to provide such a full color image with the organic EL, generally, an organic light-emitting layer is painted in red, green, and blue, independently and partially, by a vapor-deposition method employing a shadow mask, so as to provide the red pixel, the green pixel, and the blue pixel. This method, however, has problems of low processing accuracy of the shadow mask, low alignment accuracy of the shadow mask, and an increase in the size of the shadow mask.
Particularly, in a field of a large display (such as a television), a larger size of a substrate has been demanded (e.g., from G6 to G8 or G10). According to the conventional method, it is necessary to prepare a mask having a size which is equal to or larger than the size of the substrate. For this reason, it is necessary to manufacture or process a mask in accordance with the size of such a large substrate. However, the mask should be made from a significantly thin metal film (generally, a film thickness in a range of 50 nm to 100 nm). Accordingly, it is difficult to manufacture a large mask. Further, the conventional method also has problems in manufacturing and processing a mask in accordance with a large substrate. Low processing accuracy and low alignment accuracy cause light-emitting layers to be mixed with each other (i.e., a mixture of colors). In order to prevent this problem, generally, it is necessary to cause an insulating layer provided between pixels to have a wide width. Accordingly, in a case where each of the pixels has a predetermined area, there is a reduction in area of a light-emitting section. This causes a reduction in aperture ratio of the pixels. Such a reduction in aperture ratio results in a reduction in luminance, an increase in power consumption, and a reduction in a lifetime of the display. Further, according to a conventional production method, an organic layer is formed in such a manner that (i) a vapor-deposition source is provided below a substrate, and (ii) an organic material is vapor-deposited on substrate in an upward direction. With the method, however, the larger the substrate (the mask) becomes, the greater a flexure of the mask becomes in a center of the substrate. The problem of the flexure also causes the mixture of colors. Further, there is a case where the substrate has a part where no organic layer is provided due to significant flexure of the mask. This causes a leakage of a current between electrodes, and such a leakage results in a defect of the display. In addition, according to the conventional method, when the mask is used a certain number of times, the mask is deteriorated. It is impossible to use the mask thus deteriorated. Accordingly, the larger the mask becomes, the higher a production cost of the display becomes. The increase in production cost is regarded as the biggest problem in the field of the organic EL display.
In view of the problems, there has been proposed a method of manufacturing a large display by combining a plurality of organic EL displays with each other. However, in a case where a plurality of panels are combined with each other, connected edges of the plurality of panels are viewable to a viewer. This reduces display quality of the display. In order to solve the problem, Patent Literature 1 proposes a technique of further sealing four panels from a backside of the four panels. Although an aperture ratio becomes low with this technique, the problem of the connected edges viewable to the viewer is solved. Further, Non-patent Literature 1 proposes a method of eliminating the problem of the connected edges viewable to the viewer by (i) causing two panels to overlap each other so that sealing sections of the two panels overlap each other, and (ii) attaching, to one of two substrates of the two panels, a transmissive plate which is adjusted in refraction index.